The Hydrosilylation and Cyanosilylation of Ketones Catalyzed using Metal Borohydrides

Aim and Objective: The hydrosilylation reaction of carbonyl compounds has emerged as a powerful method in organic synthesis. The catalytic hydrosilylation of ketones is a valuable transformation because it generates protected cyanosilylation reaction of carbonyl compounds is an efficient procedure for the synthesis of silylated cyanohydrins, which are readily converted into useful functionalized compounds, such as cyanohydrins, α-hydroxy acids, β-amino alcohols and other biologically active compounds. Materials and Methods: A facile, economic and efficient method has been developed for the hydrosilylation and cyanosilylation of ketones using metal borohydrides. A series of silylated ethers and silylated cyanohydrins can be isolated via direct distillation. Results: The catalytic properties of a range of metal borohydrides in the hydrosilylation reaction of acetophenone with diphenylsilane were investigated. The relative catalytic activity of the borohydride catalyst studied was as follows: (CH3)4NBH4> (PhCH2)(CH3)3NBH4> (CH2CH3)4NBH4> (CH3CH2CH2CH3)4NBH4> NaBH4> KBH4> LiBH4. The cyanosilylation of acetophenone using trimethylsilyl cyanide (TMSCN) in the presence of NaBH4 occurred under similar reaction conditions. An excellent reaction rate and high conversion were obtained. Conclusion: The metal borohydride-catalyzed hydrosilylation alcohols in one step. The and cyanosilylation of ketones could be carried out smoothly under mild reaction conditions. Among the metal borohydrides studied, an excellent reaction rate and high conversion were obtained using NaBH4, NaBH (CH2CH3)3 or (alkyl)4 NBH4 as the reaction catalyst.

DECOMPOSITION OF SODIUM HYPOCHLORITE: THE CATALYZED REACTION

The catalyzed decomposition of sodium hypochlorite has been examined; the catalysts tried were manganese, iron, cobalt, nickel, and copper oxides. It was shown that in no case was the decomposition to chlorate and chloride accelerated, only the reaction to chloride and oxygen. Manganese and iron did not catalyze even the latter reaction, or only to a very small extent; this was in fairly concentrated sodium hypochlorite containing some sodium hydroxide. The manganese and iron are largely oxidized to permanganate and ferrate under these conditions. It was found that copper could catalyze the formation of permanganate and ferrate, and nickel the formation of permanganate. Cobalt catalyzed the reaction going to oxygen, and the rate was proportional to the cobalt added, but little dependent on the hypochlorite concentration; the same is true of nickel. Copper (as reported earlier) gives a catalyzed reaction not far from first order in hypochlorite. The activation energies were measured, and were consistent with the relative catalytic activity of these metals. The mechanism of the reaction is briefly discussed.